On the utilitarian front, this 5-pack of FosPower 3-ring male-to-female headphone jack adapters is on sale for $9 by the seller FosPower with the order fulfilled by Amazon, so it is Prime eligible. As of the time of writing they are not an Add-On item, so you get free 2-day shipping as a Prime member without having to buy anything else.
The 5-pack is currently the best per-unit price among the other options (they have 1-pack, 3-pack, this one, and 10-pack).

These maybe handy if you have phones or DAPs or other devices or headphones with “difficult” 3.5mm situations. All together, they average 4.2 out of 5 with nearly 350 customer reviews, and have over 60 questions answered. They have a 7-to-1 “review intensity ratio” (5-stars vs 1-stars) so it’s a good idea to check some of the 1-star reviews to see what issues people had with these.

PS: typically a double figure “review intensity ratio” (10:1 or better) is a sign of a lower risk purchase, but again, the heuristic metrics are only as good as the underlying reviews, and there’s no guarantee of review quality or consistency from product to product.